Herpes simplex virus remains a significant public health threat despite the availability of antivirals to treat HSV infections. The incidence of genital HSV infection has doubled in the last decade and it is estimated that 22% of all people over 12 years of age in the US are infected with HSV-2. HSV infection also is a significant risk factor for acquisition of HIV infection. It has been known for some time that the presence of ulcerative genital disease increases. Since both HIV and HSV cause persistent infections, the ideal control strategy is to prevent infection. Many people choose not to use condoms and nonoxynol-9 enhances HIV infection by damaging the vaginal mucosa. Alterative preventative strategies are desperately needed. The applicant has discovered a series of peptides that block HSV infection in vitro and one, EB, which is virucidal, also blocks infection in vivo. The applicant?s collaborators have shown that the peptides also block HIV and HPV infection. The first overall goal of Project II is to further the development of the lead peptides that the applicant has discovered and move them closer to clinical trials. He will determine the mechanism of action of the peptides, screen derivatives to identify more potent peptides, test in vitro toxicity in several cell types, and test efficacy in an animal model of HSV epithelial disease. The second overall goal is to use the peptides as tools to study processes involved in HSV entry. The applicant will test binding of the antiviral peptides to the purified entry proteins of HSV(gB, gD, and gH/gL), use the peptides to block entry and analyze the step or steps that are blocked. He will use phage display methods in conjunction with Core A to identify peptides that specifically bind to the purified glycoproteins. These peptides will then be tested for antiviral activity and used in studies to determine the role of the proteins in entry .